PySolFC - PySolFC is a collection of more than 1000 solitaire card games. It is a fork of PySol Solitaire.
Solitaire.gg - Massive open-source solitaire project with hundreds of games.
NetSolitaire - Play Klondike, FreeCell, Spider and many other solitaire games online for free in your desktop or tablet browser
Pasjans Solitaire - A very elegant, cross-platform solitaire suite for both online and offline play.
Solitaire Lounge - Solitaire Lounge is a spin-off for the classical game of Solitaire with amazing animated themes.
World of Solitaire - Over 50 beautiful free web based Solitaire games. Klondike, Spider, FreeCell and more.